Hi, I have a 2014 Cls 550. I replaced the battery, alternator, and serpentine belt at the same time, but, battery is still not charging. Dreaded red battery light on instrument cluster stating "see owners manual". Suggestions? Does this model Mercedes have an alternator fuse, relay, or fuse link?

My initial guess is your new Alt is bad, it happens. Or perhaps you have a connector that isn't quite plugged in all the way.

Regardless, first verify the symptom. With the engine and ignition off use a multi meter to check battery voltage at the + and - battery terminals. Then start the engine and check again. With the engine running battery voltage should be higher than when the engine is not running.